The process by which the mammalian immune system recognizes and reacts to foreign or alien materials is complex. An important facet of the system is the T cell response. T cells can recognize and interact with other cells via cell surface complexes on the other cells of peptides and molecules referred to as human leukocyte antigens ("HLA") or major histocompatibility complexes ("MHCs"). The peptides are derived from larger molecules which are processed by the cells which also present the HLA/MHC molecule. See Male et al., Advanced Immunology (J.P. Lipincott Company, 1987), especially chapters 6-10. The interaction of T cells and complexes of HLA/peptide is restricted, requiring a specific T cell for a specific complex of an HLA molecule and a peptide. If a specific T cell is not present, there is no T cell response even if its partner complex is present. Similarly, there is no response if the specific complex is absent, but the T cell is present. The mechanism is involved in the immune system's response to foreign materials, in autoimmune pathologies, and in responses to cellular abnormalities.
The mechanism by which T cells recognize alien materials also has been implicated in cancer. A number of cytolytic T lymphocyte (CTL) clones directed against autologous melanoma have been described. In some instances, the antigens recognized by these clones have been characterized. In PCT application PCT/US92/04354, published on Nov. 26, 1992, the "MAGE" family, a tumor specific family of genes, is disclosed. The expression products of these genes are processed into peptides which, in turn, are expressed on cell surfaces. This can lead to lysis of the tumor cells by specific CTLs. The genes are said to code for "tumor rejection antigen precursors" or "TRAP" molecules, and the peptides derived therefrom are referred to as "tumor rejection antigens" or "TRAs". See Traversari et al., Immunogenetics 35: 145 (1992); van der Bruggen et al., Science 254: 1643 (1991), for further information on this family of genes. Also, see U.S. Pat. No. 5,342,774.
In U.S. Pat. No. 5,405,940, MAGE nonapeptides are taught which are presented by the HLA-A1 molecule. Given the known specificity of particular peptides for particular HLA molecules, one should expect a particular peptide to bind one HLA molecule, but not others. This is important, because different individuals possess different HLA phenotypes. As a result, while identification of a particular peptide as being a partner for a specific HLA molecule has diagnostic and therapeutic ramifications, these are only relevant for individuals with that particular HLA phenotype. There is a need for further work in the area, because cellular abnormalities are not restricted to one particular HLA phenotype, and targeted therapy requires some knowledge of the phenotype of the abnormal cells at issue.
It also was discovered that a MAGE expression product is processed to a second TRA. This second TRA is presented by HLA-C clone 10 molecules. Therefore, a given TRAP can yield a plurality of TRAs.
In PCT WO94/14459, published Jul. 7, 1994, tyrosinase is described as a tumor rejection antigen precursor. This reference discloses that a molecule which is produced by some normal cells (e.g., melanocytes), is processed in tumor cells to yield a tumor rejection antigen that is presented by HLA-A2 molecules.
In PCT WO94/21126, published Sep. 29, 1994, a second TRA, not derived from tyrosinase is taught to be presented by HLA-A2 molecules. The TRA is derived from a TRAP, but is coded for by a non-MAGE gene. It is called Melan-A. This disclosure shows that a particular HLA molecule may present TRAs derived from different sources.
In PCT WO95/00159, published Jan. 5, 1995, an unrelated tumor rejection antigen precursor, the so-called "BAGE" precursor, is described. TRAs are derived from the TRAP and also are described. They form complexes with MHC molecule HLA-C-Clone 10.
In PCT WO95/03422, published Feb. 2, 1995, another unrelated tumor rejection antigen precursor, the so-called "GAGE" precursor, is described. The GAGE precursor is not related to the BAGE or the MAGE family.
The work which is presented by the papers, patents and patent applications described above deal, for the most part, with the MAGE family of genes, the BAGE gene and the GAGE gene. These genes are expressed in a number of tumors but are completely silent in normal tissues except testis. None is expressed in renal carcinoma.
Recently another unrelated tumor rejection antigen precursor, the "RAGE" precursor, was discovered. It is distinguished, inter alia, by its expression in certain renal carcinomas. The RAGE precursor is not related to the GAGE, BAGE or MAGE family.
The brain glycogen phosphorylase gene is normally expressed in the adult in brain and retinal pigment epithelium. It previously was reported that this gene was over-expressed in certain renal, hepatoma and stomach cancers. It was not reported, however, that the brain glycogen phosphorylase gene was capable of provoking autologous CTL proliferation with specificity for brain glycogen phosphorylase peptides complexed with HLA. In other words, brain glycogen phosphorylase was not known as a TRAP.
It has now been discovered that the brain glycogen phosphorylase gene is expressed in melanoma tumor cells, and in certain other tumor cell types. It now has been discovered that, the brain glycogen phosphorylase gene, encodes tumor rejection antigens and precursors thereof. The brain glycogen phosphorylase gene does not show homology to the MAGE family of genes, to the BAGE gene, the GAGE gene or to the RAGE gene.
The invention is elaborated upon in the disclosure which follows.